Upgrade to OpenSSL 0.9.8h.
[dragonfly.git] / secure / lib / libcrypto / man / DH_generate_parameters.3
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129.\" ========================================================================
130.\"
131.IX Title "DH_generate_parameters 3"
aac4ff6f 132.TH DH_generate_parameters 3 "2008-09-06" "0.9.8h" "OpenSSL"
984263bc 133.SH "NAME"
8b0cefbb 134DH_generate_parameters, DH_check \- generate and check Diffie\-Hellman parameters
984263bc 135.SH "SYNOPSIS"
8b0cefbb 136.IX Header "SYNOPSIS"
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137.Vb 1
138\& #include <openssl/dh.h>
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139.Ve
140.PP
141.Vb 2
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142\& DH *DH_generate_parameters(int prime_len, int generator,
143\& void (*callback)(int, int, void *), void *cb_arg);
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144.Ve
145.PP
146.Vb 1
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147\& int DH_check(DH *dh, int *codes);
148.Ve
149.SH "DESCRIPTION"
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150.IX Header "DESCRIPTION"
151\&\fIDH_generate_parameters()\fR generates Diffie-Hellman parameters that can
984263bc 152be shared among a group of users, and returns them in a newly
8b0cefbb 153allocated \fB\s-1DH\s0\fR structure. The pseudo-random number generator must be
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154seeded prior to calling \fIDH_generate_parameters()\fR.
155.PP
8b0cefbb 156\&\fBprime_len\fR is the length in bits of the safe prime to be generated.
aac4ff6f 157\&\fBgenerator\fR is a small number > 1, typically 2 or 5.
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158.PP
159A callback function may be used to provide feedback about the progress
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160of the key generation. If \fBcallback\fR is not \fB\s-1NULL\s0\fR, it will be
161called as described in \fIBN_generate_prime\fR\|(3) while a random prime
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162number is generated, and when a prime has been found, \fBcallback(3,
1630, cb_arg)\fR is called.
164.PP
8b0cefbb 165\&\fIDH_check()\fR validates Diffie-Hellman parameters. It checks that \fBp\fR is
984263bc 166a safe prime, and that \fBg\fR is a suitable generator. In the case of an
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167error, the bit flags \s-1DH_CHECK_P_NOT_SAFE_PRIME\s0 or
168\&\s-1DH_NOT_SUITABLE_GENERATOR\s0 are set in \fB*codes\fR.
169\&\s-1DH_UNABLE_TO_CHECK_GENERATOR\s0 is set if the generator cannot be
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170checked, i.e. it does not equal 2 or 5.
171.SH "RETURN VALUES"
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172.IX Header "RETURN VALUES"
173\&\fIDH_generate_parameters()\fR returns a pointer to the \s-1DH\s0 structure, or
174\&\s-1NULL\s0 if the parameter generation fails. The error codes can be
175obtained by \fIERR_get_error\fR\|(3).
984263bc 176.PP
8b0cefbb 177\&\fIDH_check()\fR returns 1 if the check could be performed, 0 otherwise.
984263bc 178.SH "NOTES"
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179.IX Header "NOTES"
180\&\fIDH_generate_parameters()\fR may run for several hours before finding a
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181suitable prime.
182.PP
183The parameters generated by \fIDH_generate_parameters()\fR are not to be
184used in signature schemes.
185.SH "BUGS"
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186.IX Header "BUGS"
187If \fBgenerator\fR is not 2 or 5, \fBdh\->g\fR=\fBgenerator\fR is not
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188a usable generator.
189.SH "SEE ALSO"
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190.IX Header "SEE ALSO"
191\&\fIdh\fR\|(3), \fIERR_get_error\fR\|(3), \fIrand\fR\|(3),
192\&\fIDH_free\fR\|(3)
984263bc 193.SH "HISTORY"
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194.IX Header "HISTORY"
195\&\fIDH_check()\fR is available in all versions of SSLeay and OpenSSL.
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196The \fBcb_arg\fR argument to \fIDH_generate_parameters()\fR was added in SSLeay 0.9.0.
197.PP
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198In versions before OpenSSL 0.9.5, \s-1DH_CHECK_P_NOT_STRONG_PRIME\s0 is used
199instead of \s-1DH_CHECK_P_NOT_SAFE_PRIME\s0.